U.S. Sen. Cory Gardner brought in $3.6 million for the year’s second quarter, and the Colorado Republican had $10.68 million cash on hand – more than twice the money his Democratic challenger, former Gov. John Hickenlooper, had in the bank at the end of the period.

Hickenlooper, who won an expensive primary by a wide margin on the last day of the quarter, plans to report raising $5.2 million between April 1 and June 30 and will report $4.6 million on hand, his campaign said.

The Democrat’s total contributions are a record quarterly haul for a Colorado Senate candidate, beating the previous record of $4.3 million raised by Gardner in the 3rd quarter of 2014, when he was on his way to unseating Mark Udall, the Democratic incumbent.

“The Gardner campaign enters the general election with a massive advantage over Hickenlooper’s campaign, with our campaign reporting more than double Hickenlooper’s cash on hand,” Gardner campaign manager Casey Contres told Colorado Politics in a statement. “Hickenlooper’s campaign continues to burn through cash at an alarming rate to bail out their ethics-plagued candidate.”

Hickenlooper, who joined the race in August after a failed presidential bid, has raised more money than Gardner in each of the last three quarters, but his cash-on-hand total has lagged the incumbent’s over the same period.

Gardner, seeking his second term, is considered the most vulnerable Republican senator on the ballot this year, but his campaign and his allies have been hammering Hickenlooper over rulings in June that the popular former two-term governor violated a state ethics ban and was found in contempt by the state’s ethics commission.

“We will need every bit of grassroots help as the Republican cavalry comes in to try to save Senator Cory Gardner with millions of dark money and corporate PAC dollars,” said Hickenlooper, who has sworn off direct contributions from corporate political action committees, in a statement.

“But Mitch McConnell and his friends can’t change one simple fact: Senator Gardner has sided with Trump 100% of the time and failed to be the independent voice he promised Coloradans he’d be. We need a change in Washington, and with the backing of our grassroots donors and volunteers we’re going to deliver that change in November.”

Quarterly campaign finance reports for federal candidates are due to the Federal Election Commission by 10 p.m. Wednesday.

In total, Gardner has raised roughly $17.2 million since taking office in 2015, and Hickenlooper has raised about $14.2 million in the 10 months he’s been in the race.

In the 2014 election, Udall raised about $20 million and Gardner raised about $12 million, but spending by outside groups totaled more than $70 million.